Radio transmitter



Aug. 9, 1932.

L. A. GEBHARD RADIO TRANSMITTER Filed March 26. 1929 2 Sheets-Sheet l INVENTOR. S20/184x399 61, Qamc,'

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TTORNEY Aug 9, 1932 L. A. GEBHARD 1,870,678

RADIO TRANSMITTER Filed March 26, 1929 2 Sheets-Sheet 2 INI/EN TOR.

ATTORNEY Patented Aug. 9, 1932 UNITED "STATES .PATENT oFFIcr,

LOIS A. GERHARD, F WASHINGTON, DISTRICT OF 'CLUMBIA ASSIGNOR TOKWIRED RADIO, INC., OF NEW YORK, Y.,

A CORPORATION 0F DELAWARE RADIO TRANSMITTER Application led March 26, 1929. Serial No. 350,049'.

My invention relates broadly to radio transmitters generally and more particularly tovcontrol circuits of thermionic tube transmitting systems.

"f One of the objects of my invention is to and by reference to the accompanying drawings, wherein: j A

Figuresl and 2 are schematic circuit diagramsshowing different modifications of the improvements in radio transmitters of my invention.

In thermionic tube transmitters operating -at very high frequencies, and especially when high power water cooled tubes are employed as amplifiers, it is not unusual under operatl`i5-0 'ino conditions to have the biasinfy current in Vthe control electrode circuit reverse its normal direction of flow. As is well known to those skilled inthe art, thermionic tubes when employed as amplifiers of high frequency electrical energy must be operated at the proper portion of their characteristic curve. `This portion of the curve is called the dynamic portion, beingk that portion where substantially like changes of plate cur- -`4 rent are caused by substantially corresponding changes of the potential supplied the control electrode. To maintain the normal control electrode potential at the proper value whereby` the tube operates efficiently as a "5 high frequency amplifier, it is usual to provide a potential for the control electrode whereby the control electrode is alwaysmainktained at a direct current bias potential of vnegative polarity with'respect to the cathode. "5.0 Should such control electrode biasing potential be removed, the control electrode would be more positive with respect to the cathode. This increase of positivepotential impressed upon the control electrode would cause an eX- cessive increase of current in the anode circuit which would destroy, or at least damage, the thermionic tube.

The improvements 1n radio transmitters of my invention provide suitable protection for the thermionic tube, should such abnormal condition arise, as previously referred to. `The current in the control electrode circuit ymay reverse its normal direction of flow. This causes an abnormal rise of anode current, and damage or possibly destruction of the tube may result.

y The improvements in radio transmitters of my invention provide suitable protection should this condition arise. Itis well known to those skilled in the art that under certain l conditions the current in the control electrode circuit does reverse its normal direction in thermionic tubes operating at high frequency, and while the theory regarding such actionis not definitely understood, the effect is nevertheless known to those skilled in the art. i

Fig. l of the accompanying drawings shows one modification of the improvements in the radio. transmitters of my invention. The circuit diagrams shown herein are schematic and are only for the purpose of explaining the arrangements and operation. Thermionic tube l is connected with an input circuit and an output circuit. The input circuit has a frequency stabilizing device whereby the generated high frequency energy is substantially constant. rlhe output of tube l is delivered to the input circuit of thermionic tube 2. The output of thermionic tube 2 is delivered to the input of tube 8. The output Vvof tube 3 is delivered to the input circuitv of tube 4 and the output circuit of tube 4 is delivered to load circuit 25. Load circuit 25 may be a space radio radiating system as shown, or physical circuits as* `employed. in wired radio systems. The cathode circuits are energized by source 26. VThe anode circuits are energized by sources 27 and 17.

Control Velectrodebiasing potential is sup-r plied to thermionic tube 4 from source 10.

M sign, having windings 7 Vand ,7a connected'in Source of energy 14 serves to supply the potential for energizing the several relay cirf cuits. Y

The control electrode circuit for tube 4 is controlled in accordance with my invention since it is usually the high power tube which is subject tothe abnormal condition heretofore mentioned. It is obvious, however, that like control means may be provided forthe control electrode circuits of any' number of tubes in the transmitter irrespective of their associated circuit and mode of operation. A

relay 6 is provided, which is of polarized deseries with the control electrode of thermionc tube 4, resistance 5, meter y28 and "source-10.

i Meter 28 may be of the ampere or milliampere ytothe operator bythe lmeter vane.

range and need not be included in the circuit unless desired. The` current inthe control electrode circuit is indicated bymeter 28 vand reversal of the normal direction isindicated Should the direction ofthe current reverse, it is improbable that the attendant operator wouldV close down theV setin time to preventdamage to tube 4. TheV relay 6 is vprovided` with an armature 6a, electromagnetically actuated thereby, carrying suitable contact members in ositions adjacent to Contact members 8 andp 9. Armaturea'ma'y be normally maintained in neutral position whereby contact members 8 and 9 are not contacting with armature 6a when the transmitter is not in operation. This opens the Acircuitffrom source 14v to momentary contact switch 11, whereb actuation of switch 11 will not enerf gize re ay 12. When source 10 is energized or the circuit supplying the control electrode biasing Yenergy is completed, armature `6a is v actuated. 'Y

The movement of armature 6a will not be suiiciently great, however, to close contacts n 8 until the energizing potential from source 10 reaches a given value. When the potential r'omvsource 10 is of sufficient value armature V"6a contacts with contact members 8, thereby completing the circuit to switch 11. Switch button 11a can now be closed thereby com-y pletingthe circuit from source 14 to electromagnet 12. Electromagnet 12factuates contacting armatures 15, 16. Contact members 15 arevengaged whereby the energizing circuit to electromagnetV 12 is Ycompleted when switch button 11a is released. Resistance 13 is connected in series with source 14 and electromagnet 12, and serves to limit ythe current through' electromagnet 12. Contacting armature 16 is electromagnetically 'actuated by electromagnet 12 and electrically connected in series with source 17 and the anode circuit of thermionic tube 4. In Fig. l, series feed anvode .supply through inductance 18 is shown, 1however, it is obviousthat Vcircuits may be employed.

arallel supply hould the current in the control electrode 4circuit reverse f paral button 11a is released. Contacting armatureV .tacting armature 16.

its normal direction of flow, armature 6a would not be attracted' to contact member 8 and the energizing circuit of electromagnet 12 would be opened. This would cause contacting armature 16 to open thereby disconnecting the circuit from source 17 to the anode of thermionic tube 4. Observation of the current measuring device 28 would indicate that'theV current in the control electrode circuit had changedin that it had reversed its normal direction of flow.

Fig. 2 of the drawings shows another modificat1onof the improvements in the radio transmitters of Vmy invention. VReference characters employed in Fig. 2 correspond to those of Fig. 1. In Fig. 1, contact member 9 was notshownconnected to any circuit; this contact kmember may however be connected with any suitable indicating lamp or the like. In the schematic' circuit diagram shown in Fig. 2, contact member 9 is connected to one terminal of electromagnet 12 while armature 6a is connected tothe remainingterminal. Switch 11 completes the energizing circuit to electromagnet 12 when switch button 11a` is depressed.v Contacts 15k are connected in el and complete the circuit when switch Many `modiications of my invention are possible such as the number of tubesemployed land'sources of energizing potential, without departing from thespirit of m invention. It is to be clearly understood ytliat the embodiments of my invention are not in any manner tobe restricted Vby the accompanying drawings or by ythe f foregoing specication but only by the scope of the appended claims.

What I claim as new and desire' to secure by Letters Patent of the Unitedy States is as follows: f e

f 1. Ina radio transmitterfa thermio `crtube,

'a source of control electrode biasing potential, a source of anode potentiaha polarized -relay having its winding connected in series -with said source of biasing potential and the cont-rol electrode of said thermionic tube, said relay having a polarized armature and associated contacts connected to control the appliycation of anode supply potential to said thermionic tube in accordance with the direction of current Howing in the winding offsaid relay. 1

2. In Va radio transmitter, a thermionic tube, a source of anode potential, a source of control'electrode biasing potential, a polarized relay having its activating winding connected between said source of biasing potential and the control electrode of said tube, an electromagnetic circuit breaker having its contacts connected between said source of anode potential and the anode of said tube, the activating winding of said circuit breaker being connected to the contacts of said polarized relay through a source of potential, whereby the opening of the contacts of said relay opens the circuit of the activating winding of said circuit breaker.

3. In a radio transmitter, a thermionic tube, a source of anode potential, a source of control electrode biasing potential, a polarized relay having its activating winding connected between said source of biasing potential and the control electrode of said tube, an electromagnetic circuit breaker having its contacts connected between said source of anc ode potential and the anode of said tube, a source of potential connected to the activating winding of said circuit breaker, the contacts of said polarized relay being respectively connected to the terminals of the activating winding of said circuit breaker for short circuiting the activating winding of said circuit breaker when the contacts of said polarized relay are closed. Y

LOUIS A. GEBHARD. 

